<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<script>
    function fn(){
        let a = b = 100;
        window.x = y = 101;
    }
    fn();
    console.log(b,x,y);

</script>
</body>
</html>